WM8959 datasheet(32/155 Pages) WOLFSON

номер детали	WM8959

подробное описание детали	Mobile Multimedia DAC with Dual-Mode Class AB/D Speaker Driver

PDF	155 Pages

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производитель	WOLFSON [Wolfson Microelectronics plc]

домашняя страница	http://www.wolfsonmicro.com

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32 / 155 page

WM8959

Pre-Production

PP, May 2008, Rev 3.1

INTERNAL POWER ON RESET CIRCUIT

Figure 12 Internal Power on Reset Circuit Schematic

The WM8959 includes an internal Power-On-Reset Circuit, as shown in Figure 12, which is used to

reset the digital logic into a default state after power up. The POR circuit is powered from AVDD and

monitors DCVDD. It asserts PORB low if AVDD or DCVDD is below a minimum threshold.

Figure 13 Typical Power up Sequence where AVDD is Powered before DCVDD

Figure 13 shows a typical power-up sequence where AVDD comes up first. When AVDD goes above

the minimum threshold, Vpora, there is enough voltage for the circuit to guarantee PORB is asserted

low and the chip is held in reset. In this condition, all writes to the control interface are ignored. Now

AVDD is at full supply level. Next DCVDD rises to Vpord_on and PORB is released high and all

registers are in their default state and writes to the control interface may take place.

On power down, where AVDD falls first, PORB is asserted low whenever AVDD drops below the

minimum threshold Vpora_off.

WM8959 датащи(PDF) 32 Page - Wolfson Microelectronics plc